B. H. Roberts cites the Book of Mormon as an ancient witness to the divinity of Christ.
B. H. Roberts, "A New Testimony for Jesus," in Rasha — the Jew: A Message to All Jews (Salt Lake City: The Deseret News Press, 1932), 56–101
We will say for the purpose of this writing that the previous papers I have written are judged by you to be inadequate to their purpose—your conversion to the belief that Jesus of Nazareth fulfills the requirements of the prophecies of your Scriptures. So let it stand for the present. But I have another Witness for my truth: and “Rasha”, the Jew, hearken to this Witness, I pray you.
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And now “Rasha”, comes the serious part of my message to you, and to all my brethren of Judah. The thing I have been “supposing” respecting the “Manuscript Record”, and its testimony here considered is reality, though under slightly different conditions than those named under the “supposed case”. Instead of a “Manuscript Record” the Record was, and is engraven on metallic plates—gold plates. Instead of being discovered in a temple in a Central American state, it was revealed by the coming of an angel from God, who made known its existence to be in a prominent hill, in western New York state, called by the ancient people of America “Cumorah”; and those gold plates were given into the temporary possession of one Joseph Smith, to be translated; not by the learned lore of men, but by the power of God, by means of Urim and Thummim—being a divine instrument, a means of revelation "Rasha”, for making known the things of God, not unknown among the prophets and seers of our ancient Israel. This revelation of the American Witness to the Lord Jesus Christ, and to his being the Holy One of Israel, the Messiah of the Old Testament— Jehovah incarnate—through whom is to come, nay, through whom has come—resurrection from the dead, forgiveness of sin and redemption of the world,—this Record was given to Joseph Smith of Palmyra, New York, in the third decade of the 19th century; and he translated this ancient American Scripture and published it under the title of The Book of Mormon, because it is a compilation of abridged documents, made by an ancient prophet of the western continent by the name of Mormon—about 400-420 A. D.
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In my “supposed case” of the “Manuscript Record”, I confined myself to the “Nephite” part of it because this had to do with the distinctly Israelitish part of the Book of Mormon the Hebrew colonies brought to the western world, and is the part of the book which, both prophetically and historically, deals more especially with the Christ, and the intent of the book, which is to “convince both the Jew and the Gentile, that Jesus is the Christ, the eternal God, manifesting himself unto all nations.”
This Book of Mormon, then, this new volume of Scripture, revealed of God, in the manner above detailed, is God’s New Witness to the world of the truth that Jesus is both Lord and Christ—Jehovah incarnate, God manifested in the flesh. He came to the earth in order to redeem men from sin, and to bring to pass man's spiritual re-birth into fellowship with God; and also to bring to pass man's resurrection from the dead—the reuniting of spirit and body into an immortal, physical life, in which life man will be capable of receiving a fulness of joy, and without such immortal fife—the union of spirit and element into one sole being—a personal entity—men can not receive a fulness of joy.